While the Bloomberg administration boasts that parks are in better shape than they’ve been in four decades, an investigation of 70 parks over the last nine months found:

* Clusters of homeless living in tents and small shantytowns in 10 parks, including Riverside Park near 148th Street in Manhattan.

* Hookers brazenly plying their 24-hour trade, including at Printers Park on Hoe Street in The Bronx.

* Areas where junkies shoot up and crack dealers set up shop, including at Fort George Playground in Washington Heights.

* An illegal chop shop where stolen vehicles, including a stripped US Defense Dept. sedan, are harvested is thriving in Fresh Creek Nature Preserve in Brooklyn.

* And many barren parks covered in weeds up to 12 feet high that are used as illegal dumps for items like abandoned boats and cars, construction debris, containers of hazardous material, opened steel safes, Vegas-style slot machines – and even a discarded tombstone in Dreier-Offerman Park in Brooklyn.

Dreier-Offerman in blue-collar Coney Island is one of the 10 neglected parks in which The Post found makeshift homeless camps. Shantytowns have invaded even Riverside Park, a favorite of nannies and their wards in the moneyed Upper West Side.

The other eight are Highbridge Park and Randalls Island Park in Manhattan; Pelham Bay Park and Soundview Park in the Bronx; Flushing Meadows Corona Park in Queens; and Spring Creek Park, Fresh Creek Nature Preserve and under the Brighton Beach boardwalk in Brooklyn.

Dreier-Offerman squatter James Henderson, 50, has been living in a tent near Bay 44th Street for more than 10 years and keeps warm by burning cans of Sterno, a fire hazard in the brush.

He uses a rickety old bike to peddle into nearby Bensonhurst to make a few bucks sweeping storefronts, and says he feels “safer living in a park than a homeless shelter” even though he’s been robbed at the park.

Just a few blocks east in Dreier-Offerman, some dozen Central and South American day laborers have set up a thriving community with a vegetable garden that includes squash and chili peppers. Their shelter is tents and abandoned cars.

Ecuadorian-born Manny, 30, has called this mini-village his home since he was 15. His pal Victor says the other squatters spend time boozing and getting high.

“They stay out of trouble. It’s not like they smoke crack. They want weed sometimes. I got weed,” Victor rambled.

The park is slated for a $40 million facelift, to be completed by 2011, but construction has yet to begin.

Out of the 70 parks visited, nine were packed with drug abusers using wooded areas as “shooting galleries” to inject heroin and smoking crack and marijuana.

On several visits to Highbridge Park in Washington Heights, small bands of men and women off a bike path were sucking on a crack pipe or shooting up, littering the ground with used needles.

In another instance, in broad daylight, a man taking a hit on a joint casually pulled down his pants to defecate as kids played on swings about 20 yards away.

A part-time park worker on security detail said she had been ordered by her supervisor “not to go inside the park because it’s just too dangerous.”

Even if she could patrol inside, she didn’t have a radio to report any suspicious activity or call for help. Her only city-authorized accessory was a notepad.

At Fresh Creek Nature Preserve in Brooklyn’s East New York, The Post found an active chop shop. In September, six sedans were stripped to their rotors and hiked on cinderblocks in the mosquito-infested wetlands pockmarked with hundreds of old tires as far as the eye could see.

Two weeks ago, those vehicles were gone and replaced by two other cars that also had their frame and interiors harvested. One had a US Department of Defense parking credential on its dashboard.

Geoffrey Croft, president of the watchdog group New York City Park Advocates, said the chop shop goes back at least two years to when he saw 15 different vehicles stripped at the same location.

Parks Commissioner Adrian Benepe said he was unaware of chop shops operating in any of New York’s 1,875 parks, adding that the city has ridded parks of more than 10,000 abandoned cars in the last 20 years.

In Riverside Park by the 148th Street shantytown, The Post witnessed male prostitutes hawking themselves to passers-by. A man in a woman’s wig was heard haggling over prices with a john who followed him into a secluded area off the park’s promenade.

Flesh peddlers have also moved in at Printers Park in Longwood, where tennis courts fell into disuse in the 1990’s. On an October evening, female hookers stood by a hole in a chain-link fence and coaxed customers to follow them to the far side, zigzagging around a junked dining chair, a stereo speaker and a packaging crate.

“The problem is many of our parks have been abandoned by the city, so of course they’re going to be a breeding ground for criminal activity,” said Croft.

But Benepe painted a rosier picture of the parks system.

“We can’t fix the lapses of other administrations overnight,” he said, “but there’s never been a bigger investment in parks in our city’s history.”

Benepe also said his department doesn’t favor some parts of the city over others, but an analysis of city data tells a vastly different story.

The city spends $10,694 per acre in taxpayer dollars annually to maintain and operate Manhattan parks. The other boroughs fare far worse, with Brooklyn ($10,173) second, followed by Queens ($4,676), The Bronx ($4,198) and Staten Island ($2,104).

But the best parks are usually the ones in elite neighborhoods that supplement their budgets with private dollars raised by well-heeled conservancies or government affiliated entities.

Manhattan’s Bryant Park gets $645,833 an acre and Central Park $30,952. The planned Brooklyn Bridge Park in Brooklyn Heights is set to get $178,794 an acre when it’s built.

The Brooklyn park is in line to have a $15.2 million yearly maintenance budget that would be funded by money raised through the creation of 1,400 controversial high-rise luxury condos to be built in the green space.

Project opponents fighting to keep housing out of the park argue that the budget is too inflated.

For instance, the park is budgeted for 40 sit-down lawnmowers to cover 85 acres while Brooklyn’s entire 4,515-acre park system is budgeted for 26 mowers.

Parkland takes up about 14 percent of the city’s land mass. And while park funding continued to increase with the rest of the city budget over the past four decades, it certainly didn’t rise at the same pace as other departments.

Instead, the city turned to borrowing money to keep its parks system from returning to the nightmare days of the fiscally strapped 1970s.

The city-funded portion of the Parks Department’s budget is about half of 1 percent of the city’s entire $59 billion budget. In 1960, 1.4 percent of city spending was set aside for parks.

As acres sit in neglect, the city has acquired 468 acres of new parkland since 2002 under Mayor Bloomberg and Benepe, doubling the Parks Department’s debt by borrowing $1.5 billion to expand and improve the park system. Up to another $1.8 billion is set to be borrowed for future projects through at least 2012.

The department’s biggest recent success stories include reviving parks in Harlem and the once vastly polluted Bronx waterfront, where significant improvements were made to Barretto Point Park, parkland along the Bronx River, Hunts Point Riverside Park and other green space.

But critics say the strategy is flawed and taxpayers would save money in the long term if the city relied more on funds from its general budget to regularly maintain parks.

Besides illegal dumping, among the biggest maintenance problems spotted were the conditions of grass fields and water fountains. Dozens of ball fields lacked grass because they flood regularly from poor drainage or have faulty irrigation systems. Many water fountains didn’t work.

Julius Spiegel, the commissioner overseeing Brooklyn’s parks, said a big dilemma “is it’s a lot easier to get capital money than expense funds” for maintenance repairs.

He said the parks system also relies heavily on City Council members who use discretionary funds set aside for pet projects to fix their local parks.

Among the recent success stories, he said, was a $4 million renovation of Brooklyn’s Linden Park funded by Councilman Charles Barron that brought field turf, lights and a professional track to what was once urban blight.

But Mark Rosenthal, president of Local 983 of District Council 37, which represents many of department’s rank-and-file employees, said that system is “flawed.”

He said council members benefit by having their neighborhood parks fall apart from neglect so they can swoop in and appear like heroes saving them, rather than making sure the city budgets enough money to regularly maintain them.

Benepe said city parks are better managed and have more employees than ever before, but Rosenthal and other union officials disagree.

They said what Benepe calls an 11,200-employee workforce is drastically inflated with part-timers and seasonal employees who lack the training and authority of full-time staff.

In 1970, the Parks Department employed 6,271 full-time workers, but by 2004, the number dropped to 1,842, city records show.

The city’s 2008 budget lists 3,891 full-time parks employees, but union officials said that number is deceiving because the department recently began using fuzzy math by counting seasonal employees as full-timers. They said the real total is similar to 2004’s numbers, which Benepe called “a lie.”

Critics say that among the biggest problems with department staffing is it only employs 239 “parks enforcement patrol” officers or peace officers to cover the 22,828 acres of parkland it oversees. Another 6,256 acres – including highway land, golf courses and zoos – is overseen by other entities.

But even the 239 officers is misleading because 110 of them are privately funded to be stationed at a few elite locations like Battery Park and Hudson River Park in Manhattan.

That leaves the remaining 129 employees to service more than 1,800 parks. Manhattan gets 37 of them, followed by Queens (19), The Bronx (19), Staten Island (17) and Brooklyn (16). Another 21 are assigned to citywide duties.

So, the city heavily relies on hundreds of seasonal uniformed security workers to protect its parks – many hired through a welfare-to-work program – who in some cases aren’t even allowed to go into certain sections of parks they’re assigned to because of high crime.

Benepe said maintaining law within parks is supposed to be the Police Department’s job. But he said “it’s hard for us to get the attention of the police when they have to deal with antiterrorism and other serious crime issues.”

NYPD Deputy Chief Michael Collins said cops respond “to any conditions in the parks as needed,” adding they also address a variety of issues besides felony crime including the homeless, graffiti and vandalism.

Until recently, the city had no system to track park crime except in Central Park, by far the city’s most famous and visited park and the only one with its own precinct.

Last year, there were 103 reported crimes in Central Park, a huge drop from 368 in 1990 and 127 in 2001.

Now the NYPD also tracks felony crimes in 20 other of the city’s largest parks.

A study by the nonprofit group New Yorkers for Parks found there were 308 felony crimes, including five murders, reported in the 20 parks between April 2006 and September 2007.

Flushing Meadows Corona Park in Queens led with 99 felony crimes, followed by Brooklyn’s Prospect Park with 57. The Bronx’s Van Cortlandt Park saw two homicides.

However, other park advocates say the data is flawed because so much crime goes unreported or isn’t tracked – especially misdemeanor crimes like illegal dumping.

Benepe declined to say how many of the city’s parks aren’t being regularly maintained, but former Parks Commissioner Henry Stern admits the city definitely wrote off some parks a long time ago.

“Some parks are parks in name only, so it becomes an issue of resources. Do you spend money building new ball fields or preventing illegal dumping? Building ball fields is sexier,” he said.